<p>Cutting hard rocks has a problem of high tool wear which can be solved by the liquid nitrogen (LN₂) assisted excavation. In this study, the strength-reducing effects of LN₂ treatment were studied experimentally. One free-surface on the top of rock sample was first exposed to LN₂ with exposure time ranging from 0 to 60 min. Then, uniaxial compression tests, Brazil splitting tests, and Nuclear magnetic resonance (NMR) tests were conducted on the treated samples to investigate the damage and fracturing of rocks induced by LN₂ treatment. The experimental results show that rock strength shows a significant reduction after exposure to LN₂ depending on the LN₂ treatment duration. For samples with short exposure times of about 1 min, LN₂ treatment only increases the micro pore numbers and doesn’t lead to any significant effect on the rock strength. For the exposure time up to 10 min, the second peak area of T₂ curve increases largely and the third peak occurs, indicating that macro cracks are induced (cracks are also observed on the rock surface). The uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) reduce significantly during this period. When the treatment duration time increases to 60 min, the tested rock sample loses its loading capacity. This research reveals that LN₂ treatment can be used to pre-damage rock to reduce the cost of drilling and excavation.</p>